Preheat oven to 325°F Grease cookie sheets. Combine flour, baking soda and salt in one bowl. In another bowl, cream melted butter and both the brown sugar and white sugar until well blended. Beat in the vanilla, egg, and egg yolk until the consistency is light and creamy. Mix in the flour, baking soda and salt from the other bowl until blended. Stir in the chocolate chunks by hand. Drop 1/4 cup of dough onto the prepared cookie sheets. The cookies should be about 3 inches apart as they spread a bit. Bakefor 15 to 18 minutes at 325F or until golden brown. Let sit on baking sheets for a few minutes before transferring to wire racks to cool completely.